Liquid transfer pipetting device with a factory adjustable and sealable calibration stop

ABSTRACT

A hand-held pipetter for extracting a predetermined volume of liquid from a body of liquid, including a movable piston within a piston chamber that is in fluid communication with a liquid receiving tip. An improved calibrating structure is disclosed wherein a calibrating stop is provided internally of the pipetter and threadedly attached to a piston operating plunger for limiting the return of the piston in response to an internal spring.

[4 1 May 13,1975

7/1966 Sherell.............,....1............. 222/309 ABSTRACT 5Claims, 4 Drawing Figures United States Patent 1 Roach LIQUID TRANSFERPIPETTING DEVICE WITH A FACTORY ADJUSTABLE AND SEALABLE CALIBRATION STOP[75] Inventor: William J. Roach, Foster City, Calif.

Oxford Laboratories, Foster City, Calif.

[73] Assignee:

[22] Filed: May 30, 1973 Appl. No.: 365,227

[30] Foreign Application Priority Data Apr. 16, 1973Germany............................ 2319175 52 U.S. 73/425.6; 222/309B0113/02 73/425, 4 P, 425.6;

[58] Field of Search References Cited UNITED STATES PATENTS 3,013,435R0driques.......................... 73/4256 1 LIQUID TRANSFER PIPETTINGDEVICE WITH A FACTORY ADJUSTABLE AND SEALABLE CALIBRATION STOPBACKGROUND OF THE INVENTION This invention is related generally tohand-held liquid transfer devices, and, more specifically to suchdevices of a precision calibrated pipetting type. This application isrelated to an application by Richard D. Reed entitled, TransferPipetting Device with a Tip Ejector.

Presently available hand-held liquid pipetting instruments are of a typeillustrated in U.S. Pat. No. 3,494,201 Roach (1970). Such devicesinclude a tubelike barrel outer structure having a plunger extendingoutward of one end thereof and a piston attached to the other end of theplunger and positioned within a piston chamber. The piston chamber ismaintained in fluid communication with an aperture at an end of thebarrel handle which is shaped for frictionally engaging a detachabletip. The piston is held in a normal rest position by one or more springswithin the barrel handle. When used to transfer liquid, the pipetterplunger is depressed, the attached tip is placed in a liquid and theplunger released to draw a precise amount of liquid into the tip. Thepipetter is then removed to a container for discharge of the liquid. Theliquid is discharged from the tip by again depressing the plunger.

In order to make sure that all of the liquid is removed from the tip,many available hand-held pipetting devices provide for moving theplunger (and thus the piston) an overshoot distance from the position towhich they were moved prior to drawing liquid into the tip. Such anovershoot feature prevents an error occurring in the volume of liquidtransfer, especially with liquids of high viscosity such as serum. Thepipetter of the aforementioned U.S. Pat. No. 3,494,201 accomplished suchovershoot by the use of two springs of significantly differingstrengths.

Another approach for providing the overshoot feature is described inco-pending patent application Ser. No. 282,321, filed Aug. 21, l972. Inthis co-pending application, a single piston return spring is utilizedwithin the pipetting device while two spaced apart stops are provided onthe plunger for engaging the barrel end, the first stop to be used upondepressing the plunger prior to drawing liquid into a tip attachedthereto, and the second stop used upon discharge of the liquid from thetip with a piston overshoot distance. The two stops are selected bylateral movement of the plunger with respect to the pipetting barrelhandle as the plunger is depressed.

It is a primary object of the present invention to provide as part of ahand-held pipetter a mechanism for removing detachable tips therefromafter use and thereby to allow for such removal without an operatorhaving to touch a used tip.

It is another object of the present invention to provide an improvedinternal construction of a pipetter to permit a lateral movement of aplunger between positive stops thereof.

SUMMARY OF THE INVENTION These and additional objects are accomplishedby the various aspects of the present invention, one of which is theprovision of a cylindrical sleeve over a tube that is attached to apipetter barrel-like housing at one end and provided with means forengaging a hollow detachable plastic tip at its other end. Thecylindrical sleeve is resiliently held away from the tip holding end ofthe tube so as not to normally interfere with the engagement of a tipthereon. When a tip is desired to be removed, however, the sleeve ismanually actuated along the length of the tube to push a used plastictip off the end of the tube. Plastic tips are normally frictionallyengaged with the end of the tube but more positive means of latching mayalso be provided, the cylindrical sleeve having a capability of removingthat type of tip as well.

For the convenience of an operator, a pair of cooperating cam lobes areprovided, one attached to the pipetter barrel adjacent its tip holdingrod and the other attached to the sleeve. The spring normally holds thetwo lobes adjacent one another in a manner to provide space at the endof the tube for holding a detachable tip. When the lobe on the sleeve isrotated with respect to the barrel handle, however, that lobe rides upon the cam lobe of the barrel handle to convert the rotary motion tolongitudinal movement of the sleeve along the tube to dislodge the tipfrom the end of the tube.

The piston of the pipetter, according to another aspect of the presentinvention, terminates outside of the piston chamber in a disc whichextends across the width of the internal portion of the pipetter barrelhandle. A plunger extending through one end of the barrel handlecontacts the piston member end disc but is not integrally formedtherewith, thereby permitting lateral movement of the plunger forselecting a piston displacement volume without causing any such movementof the piston. A calibration stop is threadedly attached to the plungerinside the barrel handle. A spring normally urges the piston discagainst the plunger and the position of the callibration stops thereonthus determines how far the piston and the plunger will be forced by thespring toward said one end of the barrel handle. The calibration stopthereby determines the amount of fluid displaced in the piston duringone operation of the pipetter. The calibration stop is preferably acylindrical sleeve which is positioned to surround the plunger, thecylindrical sleeve having its end toward the piston disc closed andthreadedly attached to the plunger while the opposite open end of thecylindrical sleeve contacts an inside surface of the barrel handles saidone end for limiting travel thereof.

Additional objects, advantages and structural features of the variousaspects of the present invention will become apparent from the followingdetailed description of a preferred embodiment thereof which should betaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates in a sectional viewa pipetter including the improvements of the various aspects of thepresent invention;

FIG. 2 shows a perspective view of the outside of a portion of thepipetter of FIG. 1; and

FIGS. 3 and 4 show in an enlarged view two parts of the pipetter ofFIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring primarily to FIG. 1,an upper portion 11 of a generally cylindrical elongated barrel handlemember has a lower portion 13 threadedly attached thereto. A finger hold15 is provided integrally with the upper barrel member 11. An elongatedtube 17 having a small bore 19 is rigidly attached to an extreme end ofthe lower barrel handle portion 13. A tip member 21 is provided at theextreme end of the tube 17 and rigidly attached thereto. The outsidesurface of the tip member 21 is conically shaped, in a very specificform, for frictionally engaging an internal surface of a conicallyshaped detachable tip 23. A bore 25 is provided through the tip member21 in order to provide fluid communication between the interior of thedetachable tip 23 and the bore 19.

At the opposite end of the barrel handle member is a plunger 27 having athreaded steel member 29 encapsulated in a plastic member 31. Theextreme plunger member 31 has a first stop surface 33 extending outwardtherefrom for limiting travel of the plunger assembly 27 into the barrelhandle by engaging an extreme outside surface 35 of an end of the barrelhandle member 11. A second stop surface 37 is provided for engaging thebarrel handle end surface 35 for depressing the plunger assembly 27 asecond further distance into the barrel handle 11. A knob, not shown, isattached to the extreme end of the plunger member 31 for receiving anoperators thumb when exerting force on the plunger assembly 27 to pushit into the barrel handle member 11. When so used, the fingers of theoperators hand are normally wrapped around the barrel member 11 underthe finger hold 15.

A piston chamber 39 is formed by a steel cylindrical sleeve 41 that isrigidly attached at one end thereof to the lower barrel handle member13. A cylindrically shaped solid piston member 43 has one end thereofpositioned within the piston chamber 39 through an end cap 45 attachedto the steel sleeve 41. A resilient O- ring 47 surrounds the piston 43for fluid sealing of that end of the piston chamber 39. The opposite endof the piston chamber 39 is provided in fluid communication with thebore 19 to result in fluid communication be tween the interior ofadetachable tip 23 and the piston chamber 39.

The opposite end of the piston 43 is provided with a circular disc 49rigidly attached thereto and extending substantially entirely across thewidth of the interior portion of the barrel handle member 11. A spring51 is normally under compression to force the disc 49 and a movablemember 53 away from each other. The movable member 53 is slidable withinan aperture of a barrel member dividing piece 55 that is rigidlyattached to the barrel member 11 at its internal threads. The spring 51thus serves to hold the piston 43 at an extreme position with respect tothe piston chamber 39 and also to exert force through the slidablemember 53 against the resilient O-ring 47. A slot of the piston chamberend piece 45 in which the O-ring 47 is held is made to be smaller thanthe cross-sectional dimensions of the O- ring 47 so that the slidablemember 53 will push down upon the O-ring 47 rather than abuttingdirectly against the piston chamber end member 45. This force causes theO-ring 47 to expand against the piston 43 for improving the fluid sealtherebetween.

In order to provide a positive limited distance of travel of the piston43 out of the piston chamber 39, an adjustable calibration stop 57 isthreadedly attached to the plunger member 29. The adjustable stop 57, ina preferred form, is a cylindrical sleeve closed at the end thereof thatthreadedly engages the plunger member 29. An opposite end 59 of thecylindrical stop member 57 abuts against an inside surface of an end ofthe barrel handle member 11.

In use of the pipetting device shown in FIG. 1, the tip 23 has its freeend immersed in a liquid to be transferred to another container. Theplunger member 31 has been depressed until its stop surface 33 abuts thebarrel end surface 35. When the plunger 31 is permitted to return to itsrest position shown in FIG. 1 under the influence of the spring 51,liquid is drawn into the tip 23 as a result of the piston 43 withdrawinga distance from within the piston chamber 39. The pipetter is then movedso that the tip 23 is positioned over a container into which the liquidis to be transferred. The plunger 31 is then depressed to force theliquid out of the tip 23. For liquid discharge, it is generallypreferable to use the overshoot feature of the device by moving theplunger member 31 laterally with respect to the handle member 11 so thatthe stop surface 37 strikes the barrel end surface 35 rather than beinglimited in travel by the first stops surface 33.

The amount of liquid that is so transferred depends upon the distancethe piston 43 travels while liquid is drawn into the tip 23. This liquidvolume may be easily calibrated during the manufacture of each pipettingdevice by placing a calibrating block between the first stop surface 33and the barrel end surface 35. The plunger member 31 is then depressedto place this block under compression while the calibrating stop 57 isturned with respect to the plunger member 29 until its end 59 tightlyengages the inside surface of the barrel end. Some appropriate threadsealant, such as an epoxy resin, is applied to hold the calibration stop57 and the plunger member 29 firmly together to prevent relativerotation therebetween. Since force is exerted during use of the deviceon the engaging threads between the plunger member 29 and thecalibrating stop 57, these members are preferably made of a metal suchas stainless steel to prevent any change in the volume capability of thedevice through use and also for precision in the initial calibration.

It may also be noted that the force exerted on the O- ring 47 isincreased as the plunger assembly 27 is driven down into the barrelassembly 11 since such plunger action compresses the spring 51.Therefore, the drag on the piston 43 produced by frictional engagementwith the O-ring 47 is reduced as the piston 43 and plunger assembly 27are returned by the spring 51 to the rest position shown in FIG. 1. Thisassures a complete and smooth return of the piston 43 to its extremerest position and also reduces the wear on the O-ring 47 by reducing thefrictional drag thereon through at least a portion of the operatingcycle.

After a liquid sample has been transferred by the use of the pipettingdevice illustrated in FIG. 1, it is desirable to remove the detachabletip 23 without the operator having to touch it. Therefore, a mechanicaltip ejector is provided as part of the pipetter structure in order toreduce the possibility that contaminated liquid may be transferredthrough the hands of the operator from a used pipetter tip to some otherliquid or test apparatus. The tip ejector includes a hollowcylindrically shaped sleeve 61 positioned about the tube 17 with aspring 63 therebetween. An actuating member 65 is fixedly held to oneend of the ejecting sleeve 61. The spring 63 normally holds the actuator65 and the sleeve 61 as far against the lower barrel member 13 as itcan. in such a normal rest position, the sleeve 61 covers only a portionof the tip member 21, thereby leaving sufficient surface for positioninga detachable pipetter tip 23 thereon. The spring 63 pushes against asurface of the tip member 21 at one end and pushes against a surv faceof the actuator 65 at its other end.

The tip ejecting mechanism of the present invention may be operated bymoving the actuator 65 along the length of the tube 17 to push thedetachable pipette tip off of the pipetter end. For operatorconvenience, however, the cylindrical sleeve 61 and actuator 65 are alsomade to be rotable with respect to the tube 17. The basic pipetter andits ejecting mechanism are cooperatively designed so that such rotarymotion is converted 7) into longitudinal motion for pushing a tip 23 offthe end of the pipetter. This is accomplished by providing co operatingcam lobes 67 and 69. The cam lobe 67 is provided as an integral part ofthe actuator 65 on an internal surface thereof. A third cam lobe 71 isprovided on the actuator 65 and displaced 180 from its other cam lobe69. Only one cam lobe 67 is provided in this specific example, as partof the lower barrel handle member 13.

In the normal rest position of the tip ejector shown in FIG. 1, thelobes 69 and 71 of the tip actuator are positioned adjacent the lobe 67of the barrel handle member 13. When the actuator 65 is turned withrespect to the barrel handle member 13, however, one of the cam lobes 69or 71 of the actuator rides up onto the cam lobe 67, as shown in FIG. 2,thereby compressing the spring 63 and forcing the tip ejector sleeve 61against the tip 23. The cam lobes are preferably shaped at their tips sothat the position shown in FIG. 2 is an unstable one; that is, the lobes67 and 69 are shaped so that the force of the spring 63 will cause thelobes 67 and 69 to slip with respect to one another from the positionshown in FIG. 2 back to the rest position illustrated in FIG. 1.Additional cams could be used in order to reduce the amount of rotationthat is required to eject a tip but an increase in the number of camlobes either reduces the longitudinal travel possible of the tip ejectorsleeve 61 or makes the side slopes of the cam lobes so steep that therotatable force required to operate them is excessive. For smoothcontinuous action of the tip ejector, a low slope angle on the sides ofthe lobes 67, 69 and 71 is preferred.

Although the various aspects of the present invention have beendescribed with respect to a preferred embodiment, it will be understoodthat the invention is entitled to protection within the full scope ofthe appended claims.

I claim:

1. In a liquid transfer pipetting device that includes a hollow barrelshaped handle member, a piston chamber within said barrel, a pistonelement within said piston chamber and extending outward through one endof said piston chamber, means extending through one end of said barrelmember for imparting reciprocal motion to said piston, resilient meanswithin said barrel for normally urging said piston toward said one endof said piston chamber, and means extending from an opposite end of saidbarrel for engaging a hollow detachable tip and for providing fluidcommunication between another end of said piston chamber and an internalportion of said tip, the improvement comprising:

a disc termination of the piston at its end removed from the pistonchamber, said disc extending across the interior space of said barrelmember,

said piston motion imparting means includes a plunger extending out ofsaid one end of the barrel member through an aperture therein andengaging at its other end within the barrel member said pistonterminating disc without an attachment thereto that prevents movement ofthe plunger in a direction downward across saidhollow barrel width, thecross-sectional shapes of said plunger and said barrel member aperturecooperating toprevent relative rotation therebetween,

a calibration stop threadedly attached to said plunger within the barrelmember for limiting travel of the piston and plunger toward said one endof the barrel member by engaging an internal surface of said one barrelmember end, whereby the piston stroke can be calibrated by turning saidcalibration stop with respect to said plunger, and

means fixing said calibration stop to said plunger for preventingrotation therebetween, whereby the piston stroke is permanentlycalibrated once the calibration stop has been adjusted and fixed.

2. The improved pipetter according to claim 1 wherein said calibrationstop comprises a hollow cylindrical member surrounding said plunger,said cylindrical member being closed at one end and threadedly attachedto said plunger at said closed end, an opposite end of said cylindricalmember engaging an inside surface of said one end of said barrel memberupon the urging of said internal spring, whereby the spring returnposition of the piston is calibrated by adjusting the cylindricalcalibration stop with respect to the plunger.

3. In a liquid transfer pipetting device that includes a hollow barrelshaped handle member, a piston chamber within said barrel, a pistonelement within said piston chamber and extending outward through one endof said piston chamber, an elongated plunger extending through one endof said barrel member for imparting reciprocal motion to said piston,resilient means within said barrel for normally urging said pistontoward said one end of said piston chamber, and means extending from anopposite end of said barrel for engaging a ho]- low detachable tip andfor providing fluid communication between another end of said pistonchamber and an internal portion of said tip, the improvement comprising:

a calibration stop threadedly attached to said elongated plunger withinthe barrel member for limiting travel of the piston and plunger towardsaid one end of the barrel member by engaging an internal barrel membersurface at its said one end, whereby the piston stroke can be calibratedby turning said calibration stop with respect to said plunger, and

means fixing said calibration stop to said plunger for preventingrotation therebetween, whereby the calibrated piston stroke ismaintained.

4. The improved pipetter according to claim 3 wherein said calibrationstop comprises a hollow cylindrical member surrounding said plunger,said cylindrical member being closed at one end and threadedly attachedto said plunger at said closed end, an opposite end of said cylindricalmember engaging the inside surface of said one end of said barrel memberupon the urging of said internal spring, whereby the spring returnposition of the piston is calibrated by adjusting the cylindricalcalibration stop with respect to the plunger.

5. A method of accurately calibrating a liquid transfer device thatincludes a hollow barrel shaped handle member, a piston chamber withinsaid barrel, a piston having one end sealably inserted into said pistonchamber with its other end cooperating with an elongated plunger thatextends through an opening in one end of said handle member, a springwithin said handle member that normally urges said piston and plungertoward said one handle end, said plunger being shaped outside saidhandle member to have two ledges that may be selected to engage anoutside surface of said one handle end by lateral displacement of saidplunger, thereby to select the volume of fluid displaced by the pistonduring one inward stroke of the plunger, said calibrating methodcomprising the steps of:

threadingly attaching a piston stop member to said plunger within saidhandle member in a manner that the spring normally urges said piston andplunger to an extreme rest position wherein the said plunger has beenaccurately calibrated.

1. In a liquid transfer pipetting device that includes a hollow barrelshaped handle member, a piston chamber within said barrel, a pistonelement within said piston chamber and extending outward through one endof said piston chamber, means extending through one end of said barrelmember for imparting reciprocal motion to said piston, resilient meanswithin said barrel for normally urging said piston toward said one endof said piston chamber, and means extending from an opposite end of saidbarrel for engaging a hollow detachable tip and for providing fluidcommunication between another end of said piston chamber and an internalportion of said tip, the improvement comprising: a disc termination ofthe piston at its end removed from the piston chamber, said discextending across the interior space of said barrel member, said pistonmotion imparting means includes a plunger extending out of said one endof the barrel member through an aperture therein and engaging at itsother end within the barrel member said piston terminating disc withoutan attachment thereto that prevents movement of the plunger in adirection downward across said hollow barrel width, the cross-sectionalshapes of said plunger and said barrel member aperture cooperating toprevent relative rotation therebetween, a calibration stop threadedlyattached to said plunger within the barrel member for limiting travel ofthe piston and plunger toward said one end of the barrel member byengaging an internal surface of said one barrel member end, whereby thepiston stroke can be calibrated by turning said calibration stop withrespect to said plunger, and means fixing said calibration stop to saidplunger for preventing rotation therebetween, whereby the piston strokeis permanently calibrated once the calibration stop has been adjustedand fixed.
 2. The improved pipetter according to claim 1 wherein saidcalibration stop comprises a hollow cylindrical member surrounding saidplunger, said cylindrical member being closed at one end and threadedlyattached to said plunger at said closed end, an opposite end of saidcylindrical member engaging an inside surface of said one end of saidbarrel member upon the urging of said internal spring, whereby thespring return position of the piston is calibrated by adjusting thecylindrical calibration stop with respect to the plunger.
 3. In a liquidtransfer pipetting device that includes a hollow barrel shaped handlemember, a piston chamber within said barrel, a piston element withinsaid piston chamber and extending outward through one end of said pistonchamber, an elongated plunger extending through one end of said barrelmember for imparTing reciprocal motion to said piston, resilient meanswithin said barrel for normally urging said piston toward said one endof said piston chamber, and means extending from an opposite end of saidbarrel for engaging a hollow detachable tip and for providing fluidcommunication between another end of said piston chamber and an internalportion of said tip, the improvement comprising: a calibration stopthreadedly attached to said elongated plunger within the barrel memberfor limiting travel of the piston and plunger toward said one end of thebarrel member by engaging an internal barrel member surface at its saidone end, whereby the piston stroke can be calibrated by turning saidcalibration stop with respect to said plunger, and means fixing saidcalibration stop to said plunger for preventing rotation therebetween,whereby the calibrated piston stroke is maintained.
 4. The improvedpipetter according to claim 3 wherein said calibration stop comprises ahollow cylindrical member surrounding said plunger, said cylindricalmember being closed at one end and threadedly attached to said plungerat said closed end, an opposite end of said cylindrical member engagingthe inside surface of said one end of said barrel member upon the urgingof said internal spring, whereby the spring return position of thepiston is calibrated by adjusting the cylindrical calibration stop withrespect to the plunger.
 5. A method of accurately calibrating a liquidtransfer device that includes a hollow barrel shaped handle member, apiston chamber within said barrel, a piston having one end sealablyinserted into said piston chamber with its other end cooperating with anelongated plunger that extends through an opening in one end of saidhandle member, a spring within said handle member that normally urgessaid piston and plunger toward said one handle end, said plunger beingshaped outside said handle member to have two ledges that may beselected to engage an outside surface of said one handle end by lateraldisplacement of said plunger, thereby to select the volume of fluiddisplaced by the piston during one inward stroke of the plunger, saidcalibrating method comprising the steps of: threadingly attaching apiston stop member to said plunger within said handle member in a mannerthat the spring normally urges said piston and plunger to an extremerest position wherein the stop member engages an inside surface of saidone handle member end, holding said plunger against the force of saidspring with a predetermined distance between the outside surface of saidone handle member end and one of said plunger ledges, turning said stopmember relative to said plunger until the stop member has advancedtherealong to firmly engage the inside surface of said one handle memberend, fixing said stop member to said plunger to prevent further rotationtherebetween, and releasing said plunger, whereby the amount of fluiddisplaced in the piston chamber by one stroke of said plunger has beenaccurately calibrated.